Observation instrument with panoramic vision

ABSTRACT

An observation instrument with panoramic vision, stabilized by a gyroscopic system having inner and outer gimbals which provide corresponding rotation axes, capable of providing accurate data on the elevation and azimuth angles of the boresight and having a fixed eyepiece, characterized by the fact that its optics include two mirrors referenced to the gyroscopic system, to wit a first front plane mirror fixed directly to the inner gimbal of said gyroscopic system, set at a fixed incidence angle, having a plane parallel to the outer gimbal axis of the gyroscopic system and inclined at 45* to the inner gimbal axis of said system, and a second plane mirror referenced to the relative motion of the gyroscopic system about its outer gimbal axis, the plane of said second mirror being so disposed that it furnishes an image of said inner gimbal axis coaxially with an axis about which maximum deflection is obtained for the boresight, and a selective magnification lens system arranged between said mirrors.

United States Patent Bezu Oct. 2, 1973 OBSERVATION INSTRUMENT WITHPANORAMIC VISION [75] Inventor: Maurice Be'zu, Croissy, France [73Assignee: Societe dEtudes & de Realisations Electroniques, Ashieres,France [22] Filed: June 14, 1971 [21] Appl. N0.: 152,890

[30] Foreign Application Priority Data July 1, 1970 France 7024400 [52]US. Cl 350/16, 350/38, 356/149, 356/248 [51] Int. Cl. G02b 23/08 [58]Field of Search 350/16, 38; 356/149, 356/248, 250

[56] References Cited UNITED STATES PATENTS 3.558.212 1/1971 Ritchie350/16 FOREIGN PATENTS OR APPLICATIONS l,428,729 8/1964 Germany 350/161563217 3/1969 France 350/16 lll Primary ExaminerDavid H. RubinAtmmeyRichard Low [57] ABSTRACT An observation instrument with panoramicvision, stabilized by a gyroscopic system having inner and outer gimbalswhich provide corresponding rotation axes, capable of providing accuratedata on the elevation and azimuth angles of the boresight and having afixed eyepiece, characterized by the fact that its optics include twomirrors referenced to the gyroscopic system, to wit a first front planemirror fixed directly to the inner gimbal of said gyroscopic system, setat a fixed incidence angle, having a plane parallel to the outer gimbalaxis of the gyroscopic system and inclined at 45 to the inner gimbalaxis of said system, and a second plane mirror referenced to therelative motion of the gyroscopic system about its outer gimbal axis,the plane of said second mirror being so disposed that it furnishes animage of said inner gimbal axis coaxially with an axis about whichmaximum deflection is obtained for the boresight, and a selectivemagnification lens system arranged between said mirrors.

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MAURICE 519.20 714W 9% OBSERVATION INSTRUMENT WITH PANORAMIC VISION Thepresent invention relates to an observation instrument with panoramicvision the boresight of which is stabilized gyroscopically in order toinsulate it from parasite motion due to movement or vibration of thesupporting means (which more specifically may be a vehicle travellingthrough the air, on land or on water).

Target acquisition and subsequent accurate guidance over long distancesof missiles launched from a moving vehicle against hostile stationary ormoving targets imply the need for the aiming element of the observationinstrument to possess great stability and to be so controllable as toallow the boresight to be deflected independently of any motion of thecarrier vehicle in order to enable the image of a distant target to beacquired and held motionless in the focal plane of the observationinstrument. Since hostile targets can appear from any direction, it isof course imperative for the watching observer to be able to explore theentire surrounding space and to be able to move the direction of hisoptical boresight at very high speed in order to acquire a designatedtarget. In order to permit automatic fire control, the observationinstrument must be capable of accurately and continuously supplying dataconcerning the azimuth and elevation angles of the boresight which iskept aimed at the target.

Certain prior art gyrostabilized observation instruments include a frontmirror pivotally mounted on a horizontal shaft which is mechanicallycoupled to the inner gimbal axis of the gyroscope bymechanical meansproviding a demultiplication in the ratio of two to one.

However, because the bearings about which the mirror rotates aresupported on the outer gimbal of the gyroscope, the mirror is notconstrained to follow the relative motion of the inner gimbal, therebycausing the inertia of the gyroscope-mirror compound to vary with theelevation angle and accordingly often making itnecessary to provide aninertia compensator to ensure good stability.

An arrangement of this kind (a mirror, mechanical demultiplication andinertia compensation)increases the inertia of the gyroscope andconsequently diminishes it nutation frequency. A very flexiblesuspension between the observation instrument and the vehicle can filterout the vibration about this nutation frequency but has the disadvantageof preventingv the direction of the boresight in relation to thereference axes of the vehicle to be determined with precision. With theaim of connecting the front mirror to the gyroscope directly, otherobservation instruments employ an anamorphic type of optical systemwhich is positioned before the front mirror and produces an opticaldemultiplication ratio of two to one.

However, a device of this kind restricts the field of exploration inazimuth to the instantaneous field of the optics.

The drawback which such observation instruments have in common is thattheir field of exploration is limited by the total deflection of thefront mirror. In order to provide panoramic vision in azimuth, both theobservation instrument and the observer must be moved simultaneouslyabout a vertical axis.

It is the object of the present invention to overcome these drawbacksand to accordingly provide a fixed observation instrument withstabilized panoramic vision capable of accurately furnishing boresightelevation and azimuth angular data for processing by a fire-controlcomputer an observation instrument which is mounted on the moving andvibrating structure either directly or through the medium of a veryrigid suspension system, by providing a gyroscopic unit having a highnutation frequency a finder head which is referenced to the positions ofthe gyroscope whereby to utilize a precession torquer the stator ofwhich is supported by the finder head and not the gyroscope and to equipthe gyroscope with positional error sensors of very low weight operatingwithin a very small range about the null position optics in which thefront mirror of small weight and size is fixed directly on to thegyroscope, while retaining the possibility of obtaining severaldifferent magnifications with the same eyepiece-ring, as well aspanoramic vision, the eyepiece remaining fixed the ability to effectswitching from a second firecontrol post in order to enable theboresight to be trained very rapidly on to a target seen by a secondobserver.

The description which follows with reference to the accompanyingnon-limitative exemplary drawings will give a clear understanding of howthe invention can be carried into practice.

Inthe drawings FIG. 1 is a highly schematic perspective view of thebasic components of an observation instrument according to a firstembodiment of this invention;

FIG. 2 is an optical diagram of an angled singleobjective binocularsight FIG. 3 shows the optical path through the sight of FIG. 2 when thesame is used for monocular sighting FIG. 4 schematically depicts theelectromechanical fieldchanging system FIG. 5 is a circuit diagram ofthe system shown in FIG. 4-;

FIG. 6 shows correspondingly to FIG. 1 a gyrostabilized observationinstrument according to a second embodiment of the invention FIG. 7shows correspondingly to FIG. 1 a gyrostabilized observation instrumentaccording to a third embodiment of the invention and FIG. 8 is thecircuit diagram permitting control of the observation instrument ofFIGS. 6 and 7 from a distant post.

As shown in FIG. 1, the boresight l of the observation instrument isstabilized by a gyroscipe 2 comprising a wheel 3 rotated at very highspeed in a Cardantype assembly giving it 2 of freedom. Wheel 3 rotatesabout an axis 4 in a first or inner gimbal 5 capable of pivoting aboutan axis 6 in a second or outer gimbal 7. Outer gimbal 7 is itselfpivotally mounted about an axis 8 inside a case 9. The axes 6 and 8 aremutually perpendicular by design, and the axes 6, 8 and 4 are at alltimes mutually perpendicular, axis 4 being parallel to boresight 1.

Fixed to the inner or elevation gimbal 5 is a front mirror 10.Preferably, in order to balance the gyroscope 2 equipped with mirror 10perfectly, the axis 6 about which inner gimbal 5 pivots may be shiftedby a certain distance to the rear of the intersection point of axes 4and 8. This way of balancing the gyroscope without adding additionalcounterweights avoids increasing the weight of the gyroscope andconsequently reduces its nutation frequency.

Mounted on the inner gimbal shaft 6 of gyroscope 2 are two angulardeviation sensors 11 and 12 and, on outer gimbal shaft 8, two furthersensors 13 and 14. Torquers l and 16 are mounted on shafts 6 and 8respectively.

In accordance with a preferred embodiment, the optical system of theobservation instrument includes A front mirror coupled to gyroscope 2the plane of mirror 10 is parallel to the outer gimbal axis 8 and formsan angle of 45 with inner gimbal axis 6, whereby the boresight l is atall times co-extensive with the rotation axis 4 of gyroscope wheel 3,the image of which axis from mirror 10 merges with the inner gimbal axis6 An afocal anamorphic optical system 17 placed before front mirror 10and referenced to the relative motion thereof, whereby to cause itsoptical axis to be co-extensive with the boresight 1 the magnificationprovided by afocal anamorphic system 17 is of two along the planecontaining inner gimbal axis 6 of gyro scope 2 and of unity along theplane perpendicular to said plane and containing the outer gimbal axis 8of gyroscope 2 A main objective 18, at the image focal plane of which isa reticle 19 which materializes the boresight l;

A second plane mirror 20 referenced to the relative motions of gyroscope2 about its outer gimbal axis 8 the plane of mirror 20 is so positionedas to cause the image of the outer gimbal axis 6 of gyroscope 2 formedby mirror 20 to be co-extensive with the axis about which it is desiredto obtain maximum rotation, to wit vertical axis 21 in FIG. 1

A second objective 22 the object focal plane of which is in the sameplane as reticle l9 preferably, reticle 19 may be formed of concentriccircles in order to avoid having to restrain it about axis 21 Anerecting prism 23 rotating about optical axis 21 this prism, which is ofthe Wollaston or Pe'chan type, is slaved to the rotational movements offront mirror 10 about inner axis 6 and to those of plane mirror 20 aboutaxis 21 whereby to eliminate run-out of the image of the scene beingobserved, which run-out is caused by the combined rotations of mirrors10 and 20 A second anamorphic optical system 24 positioned along theoptical path of the observation instrument, behind front mirror 10,whereby to eliminate the anamorphic effect and permit visualobservation.

In a preferred embodiment shown in FIG. 1, the anamorphic optical system24 is positioned after the erecting prism 23. Obviously, it could beplaced immediately after the front mirror 10 provided that it is slavedto the movements thereof about inner gimbal axis 6.

In cases where the images of the scene under observation areretransmitted by a television circuit, the anamorphic effect can beeliminated by modifying the sweep of the dissector tube. Similarly, ifthe images having undergone anamorphosis are recorded by amotion-picture camera, the anamorphic effect can be eliminated uponprojection, the projector being equipped to that end with an anamorphicoptical system. 1

The second anamorphic optical system 24 is placect in the optical path,perpendicular to the first afocal anamorphic optical system 17, that isto say that the twofold magnification is in the direction of the imageof outer gimbal axis 8 of gyroscope 2 formed by erecting prism 23. i

The anamorphic optical system 24 may be placed in the same plane asanamorphic optical system l'l' provided that it is made to work in theopposite sense an angled viewing sight 25 formed by an objective 26, anintermediate prism 27 and an eyepiece 28.

Optical sight 25 is preferably a single-objective binocular sight of thekind having its optical diagram shown in FIGS. 2 and 3.

In FIG. 2, the optical sight includes an intermediate prism 27, arhombohedron 28 comprising at its top a splitter cube 29 which splitsthe optical beam 30 into two optical beams 31 and 32, and twointermediate prisms 33 and 34 which deflect optical beam 31 intoparallelism with beam 32, which beam passes through a cube 35 so as tocause the two optical beams 31 and 32 to have optical paths of equallength.

Splitter cube 29 is retractable and replaceable in any suitable mannerand as shown diagrammatically in FIGS. 2 and 3 by a cube 36 of the samethickness. In FIG. 3, replacement cube 36 renders the sight 25 monocularin order to provide maximum clarity, for instance during twilightobservations.

a Galilean system 37 which is positioned between front mirror 10 andmain objective 18 and which, when inserted into the optical path,divides the magnification of the observation instrument by its ownmagnification and increases the fields in the reciprocal ratio.

FIGS. 4 and 5 show the electromechanical field changing system which,when required, very rapidly inserts the Galilean system 37 into theoptical path of the observation instrument. 7

The afocal or Galilean optical system is mounted on a support 38centered on the optical axis 39 and is capable of very rapidly pivotingabout an axis 40 perpendicular to optical axis 39, through an angle suchthat the Galilean system occupies the position shown in dash lines.

Through reduction gear 42, an electric motor 41 energized in theappropriate sense rotates a cam 43 the rotation of which, about a shaft44 which preferably forms an extension of shaft 40, is limited by a stop45. Carried on the end of cam 43 is a pin 46 to which is pivotallyconnected a rod 47 which slidably engages into a hole formed in a pin 48pivotally mounted on the end of an arm 49 fast with rotating shaft 40 ofsupport 38. In the resting position, cam 43 and arm 49 are at an anglea. When cam 43 is rotated, clockwise for instance, about shaft 44, itcompresses a spring 50 which surrounds rod 47 and reacts against pin 48.The force exerted by spring 50 against pin 48 causes arm 49 and support38 to pivot about shaft 40 into the position shown in dash lines. A cam51 carried on the end of shaft 44, which is fast with cam 43, operates aswitch 52 the contacts of which reverse the sense in which motor 41 isenergized, whereby, when the operator again actuates switch 53, motor 41is caused to rotate in the opposite direction in order to reinsert theGalilean system into the optical path, and so on.

The motion of the Galilean system support 38 is damped by elastic stopmeans 78.

mer t body 54 about pivotal axis XX of the carrier vehicle will bedetected by sensor 11. Inner gimbal 5 of gyroscope 2, together withfront mirror 10, remains stationary, but outer gimbal 7 tends to rotateabout inner axis 6 and to thereby rotate the stator of error sensor 11.The error signals issuing from sensor 11 are amplifled at 55 andactivate a motor 56 which, through the agency of gear-typedemultiplication means 57 for example, reset the case 9 about horizontalaxis 58 in order to cancel out the error signals. The axis 58 lies alongthe optical beam reflected by front mirror 10. Case 9 is rotatablysupported on a bearing 59 mounted in a housing 60 and in its rotationcarries with it the anamorphic optical system 17 rigidly connected toit.

Any movement in azimuth of observation instrument body 54 about pivotalaxis YY of the carrier vehicle is detected by sensor 13, the gimbal 7 ofgyroscope 2 remaining stationary together with front mirror 10, but asthe case 9 pivots about YY it rotates the stator of sensor 13 aboutouter gimbal axis 8.

The error signals issuing from sensor 13 are amplified at 61 andactivate motor 62 which, through the agency of demultiplication means63, resets the housing 60 about axis YY whereby to cancel out theseerror signals. Housing 60 is supported on a bearing 64 which providespivotal motion about axis 21 in relation to the observation instrumentbody 54. The case 9, the Galilean system 37, the main objective l8 andplane mirror 20 are associated to the rotation of housing 60, and axis21 is co-extensive with the optical beam reflected by plane mirror 20.

It is to be noted that irrespective of perturbing motions of theobservation instrument about its pivotal axes XX and YY, the boresight 1stabilized by gyroscope 2 remains fixed in space and lies at all timesalong the optical axis of the observation instrument.

Deflections of the boresight l in elevation and azimuth are obtained byappropriately energizing the torquers 16 and which cause gyroscope 2 toprecess about the elevation and azimuth axes respectively. The signalsissuing from error sensors 11 and 13 are amplifled at 55 and 61 andthereafter respectively energize the motors 56 and 62, which slave thecase 9 and the housing 60 together with the respective optical equipmentto the changed orientation of boresight l.

The unlimited rotation of housing 60 about axis 21 in relation to theobservation instrument body 54 provides panoramic vision in azimuthwithout moving the angled optical sight 25.

On the other hand, the rotation of case 9 about axis 58 is limited inorder to ensure that gyroscope 2 invariably senses any azimuthal shiftsabout its outer gimbal axis 8. The non-observable space is formed by acone with an apex angle of a few degrees. Erecting prism 23 is slavedabout optical axis 21 by differential gearing 65 which sums therotations of case 9 and housing 60.

A synchro system 66 connected, on the one hand mechanically withinsupport or housing 60 to the rotation of case 9 about axis 58, and onthe other hand electri cally to error sensor 12, outputs the boresightelevation angle data. A second synchro system 67, connected mechanicallyto housing 60 and electrically to error sensor 14 outputs the boresightazimuth angle data. These data are usable for interlocking the weaponsystem with the boresight direction and for displaying the latter onindicator means.

Referring next to FIG. 6, the motor 62 which slaves the housing 60azimuthally about axis 21- is a direct drive motor,its rotor 68 beingfixed to housing and its stator 69 to the observation instrument body54. The advantage of this arrangement is that it dispenses with themechanical demultiplication means between the motor and housing 60 andthereby avoids the mechanical backlash which would introduce a time-laginto the servo control. Such a motor 62 reduces the friction moment andabove all neutralizes the rapid perturbing motions about the axis YY byproviding a zero-speederror servo action. In this arrangement thesynchro system 67 no longer functions in the differential mode asdescribed with reference to the preceding arrangement, that is to saythat it is merely coupled mechanically to housing 60. Such anarrangement relieves the load on outer gimbal axis 8 of gyroscope 2 byeliminating the error sensor 14 of FIG. 1.

Obviously, a similar type of motor may be used to slave the case 9 aboutaxis 58 and thereby make it possible to eliminate the error sensor 12 ofFIG. 1.

In order to further reduce the inertia of gyroscope 2 and increase itsnutation frequency, its precession torquers may be replaced withadvantage by a single torquer 70 since relative motions between therotor and stator of such torquer are very small byreason of the factthat case 9 and housing 60 are slaved to the orientation of gyroscope 2.By way of example, torquer 70 may be of the variable reluctance type,and its very light rotor 71 may be supported by inner gyroscope gimbal 5and its stator 72 fixed to case 9. The rotor 71 is a spherical cap madeof electrically conducting material (such as the material known by thetrade-name Armco), placed in air gaps between the pole-faces of fourmagnetic cores energized by coils- One pair of magnetic cores ispositioned in the plane formed by inner gimbal 5 of gyroscope 2 and thesecond pair is positioned in a plane perpendicular thereto.

Energizationof one of the coils tends to attract the spherical capwhereby to close the magnetic flux and apply torque to gyroscope 2,causing the same to precess.

Alternatively, two torquers may be used, with the first having its rotorfixed to inner gyroscope gimbal 5 and the second its rotor fixed toouter gimbal 7, the stators of both torquers being supported by case 9.

Similarly, in order to reduce the inertia of the gyroscope, errorsensors 13 and 11 are made low in weight since they operate about thezero point, both the case 9 and the housing 60 being slaved to gyroscope2.

In FIG. 7, which shows a third possible embodiment, the wheel 3 ofgyroscope 2 rotates about axis 4 in the inner gimbal 5 which is able topivot about the vertical or azimuthal axis 8 within outer gimbal 7.Outer gimbal 7 is pivotally mounted about the horizontal or elevationaxis 6 within the case 9. Mounted on inner gimbal 5 is the front mirror10 which is so positioned as to cause the optical beam reflected by itto merge with the elevation axis 6 of gyroscope 2 and with the rotationaxis 58 of case 9. As shown in the drawing, the axis 8 may be offset inrelation to the intersection point of axes 4 and 6 in order to balancethe gyroscope two/mirror 10 compound.

Besides the fact that the elevation axis and the housing rotation axismerge with the optical axis, this arrangement has the advantage that themost heavily loaded gimbal shaft, namely the shaft 6, is the outergimbal shaft, so that the stators of error sensor 11 and synchro system12 are supported by the case 9.

As stated precedingly, it is possible for the gunnerobserver to causethe gyroscope to precess in order to deflect the boresight, by using thecontrol means shown in the drawing as being a box 79 equipped with aballjointed handle permitting simultaneous boresight deflections inelevation and azimuth.

As shown in FIG. 8, a switch 73 cuts off the signals from the gyroscopeerror sensors into the elevation and azimuth servo channel amplifiers 55and 61 and applies the information issuing from synchro systems 74 and75 (on which an elevation and azimuth have been preset).

Via the switch 73, synchro systems 74 and 75 are electrically connectedto the synchro systems 66 and 67, respectively, which normally supplydata to the weapon system. Switch 73 additionally controls a device (notshown) which cages the gyroscope and which is preferably anelectromagnet which is caused to engage with a notch in a rod carried bythe inner gimbal of the gyroscope whereby to reset and cage thegyroscope in relation to case 9.

As soon as switch 73 is operated, all the abovedescribed operations takeplace simultaneously and the motors 56 and 62 respectively reset thecase 9 and the housing 60, to the elevation and azimuth angles set up at76 and 77, respectively, by rotating them about the axes 58 and 21respectively.

What is claimed is 1. An observation instrument with panoramic vision,stabilized by a gyroscopic system having inner and outer gimbals whichprovide corresponding rotation axes, capable of providing accurate dataon the elevation and azimuth angles of the boresight thereof and havinga fixed eyepiece, comprising in combination optics including two mirrorsforming a boresight and referenced to the gyroscopic system, to wit afirst front plane mirror fixed directly to the inner gimbal of saidgyroscopic system, set at a fixed incidence angle, having a planeparallel to the outer gimbal axis of the gyroscopic system and inclinedat 45 to the inner gimbal axis of said system, and a second plane mirrorreferenced to the relative motion of the gyroscopic system about itsouter gimbal axis, the plane of said second mirror being so disposedthat it furnishes an image of said inner gimbal axis coaxilaly with anaxis about which maximum deflection is obtained for the boresight, and aselective magnification lens system lying along the exit pupil, andarranged between said mirrors.

2. An observation instrument according to claim 1, characterized by thefact that it includes an afocal anamorphic optical system disposed aheadof the front mirror, said anamorphic system being slaved in elevationand azimuthto said front mirror and providing a magnification of two inthe direction of the plane containing the inner gimbal axis of thegyroscopic system and unit magnification in the direction of the planecontaining the outer gimbal axis of said gyroscopic system.

3. An obersvation instrument according to claim 2, characterized by thefact that the optics thereof include a second afocal anamorphic systemthe magnification axes of which are perpendicular to those of thefirstmentioned anamorphic optical system, thereby to eliminate theanamorphosis of the image obtained ahead of the eyepiece. I

4. An observation instrument according to claim 2 characterized by thefact that the afocal anamorphic system is fixed to a housing containingthe gyroscopic system and pivotally mounted about a shaft on a case theaxis of which is perpendicular to that of said housing, which housing isassociated with servo control means therefor in respect of the relativemotions of the gyroscopic system about its inner gimbal axis, the secondmirror being supported by said case, which case is itself mounted forpivotal motion about its own axis on an observation instrument body andis associated with servo control means therefor in respect of therelative motions of said gyroscopic system about its outer gimbal axis.

5. An observation instrument according to claim 4, characterized by thefact that the axis about which maximum deflection of the aim axis, orboresight, is vertical, thereby providing panoramic vision in azimath.

6. An observation instrument according to claim 4, characterized by thefact that the case pivots about a vertical axis and the housing pivotsabout a horizontal axis thereby providing panoramic vision in elevation.

7. An observation instrument according to claim 4, characterized by thefact that the gyroscopic system is provided with a double torquer havinga rotor of very low weight supported by the inner gimbal of said systemand a stator supported by the housing for said system.

8. An observation instrument according to claim 4, characterized by thefact that the gyroscopic system is associated with two torquers of whichone is provided with a rotor fastened to inner gimbal of said system andthe other with a rotor fastened to the associated outer gimbal, saidtorquers having their stators fastened to the housing containing saidsystem.

9. An observation instrument according to claim 4, characterized by thefact that the optics thereof include an erecting prism movably mountedon the optical path and slaved to the combined motions of the housingand the case about their axes whereby to eliminate image run-out.

10. An observation instrument according to claim 4, characterized by thefact that the inner gimbal of the gyroscopic system is mounted onhorizontal pivots, the outer gimbal being mounted on verticla pivots,the front mirror being supported by said inner gimbal at a positioncausing it to provide off the incident optical beam a reflected beamwhich has its axis coextensive with the outer gimbal hinge line, theslaved position of which is co-extensive with the hinge line of thepivotal housing which contains the gyroscopic system and is slavedthereto, the plane of said front mirror being parallel to said outergimbal hinge line and forming a fixed angle of 45 to the hinge line ofsaid inner gimbal.

11. An observation instrument according to claim 4, characterized by thefact that motors for servo controlling said case and housing areassociated to synchro systems for exploiting and presetting theboresight elevation and azimuth angles from a distance.

12. An observation instrument according to claim 1, characterized by thefact that it is provided with a single-objective binocular sightcomprising, between the objective and the eyepieces, a rhombohedroncomprising a splitter cube which splits the optical beam into two beamsthat travel to the two eyepieces respectively, said splitter cube beingretractably mounted and being replaceable by an ordinary cube of thesame thickness.

mechanism, said arm being actuated by a reversible motor and having itsmotions limited by stop means and fastened through a cam for actuating aswitch that reverses the direction of rotation of a motor, said switchbeing series-connected to a further switch in the motor power-supplycircuit.

i i t

1. An observation instrument with panoramic vision, stabilized by agyroscopic system having inner and outer gimbals which providecorresponding rotation axes, capable of providing accurate data on theelevation and azimuth angles of the boresight thereof and having a fixedeyepiece, comprising in combination optics including two mirrors forminga boresight and referenced to the gyroscopic system, to wit a firstfront plane mirror fixed directly to the inner gimbal of said gyroscopicsystem, set at a fixed incidence angle, having a plane parallel to theouter gimbal axis of the gyroscopic system and inclined at 45* to theinner gimbal axis of said system, and a second plane mirror referencedto the relative motion of the gyroscopic system about its outer gimbalaxis, the plane of said second Mirror being so disposed that itfurnishes an image of said inner gimbal axis coaxilaly with an axisabout which maximum deflection is obtained for the boresight, and aselective magnification lens system lying along the exit pupil, andarranged between said mirrors.
 2. An observation instrument according toclaim 1, characterized by the fact that it includes an afocal anamorphicoptical system disposed ahead of the front mirror, said anamorphicsystem being slaved in elevation and azimuth to said front mirror andproviding a magnification of two in the direction of the planecontaining the inner gimbal axis of the gyroscopic system and unitmagnification in the direction of the plane containing the outer gimbalaxis of said gyroscopic system.
 3. An obersvation instrument accordingto claim 2, characterized by the fact that the optics thereof include asecond afocal anamorphic system the magnification axes of which areperpendicular to those of the first-mentioned anamorphic optical system,thereby to eliminate the anamorphosis of the image obtained ahead of theeyepiece.
 4. An observation instrument according to claim 2 ,characterized by the fact that the afocal anamorphic system is fixed toa housing containing the gyroscopic system and pivotally mounted about ashaft on a case the axis of which is perpendicular to that of saidhousing, which housing is associated with servo control means thereforin respect of the relative motions of the gyroscopic system about itsinner gimbal axis, the second mirror being supported by said case, whichcase is itself mounted for pivotal motion about its own axis on anobservation instrument body and is associated with servo control meanstherefor in respect of the relative motions of said gyroscopic systemabout its outer gimbal axis.
 5. An observation instrument according toclaim 4, characterized by the fact that the axis about which maximumdeflection of the aim axis, or boresight, is vertical, thereby providingpanoramic vision in azimuth.
 6. An observation instrument according toclaim 4, characterized by the fact that the case pivots about a verticalaxis and the housing pivots about a horizontal axis thereby providingpanoramic vision in elevation.
 7. An observation instrument according toclaim 4, characterized by the fact that the gyroscopic system isprovided with a double torquer having a rotor of very low weightsupported by the inner gimbal of said system and a stator supported bythe housing for said system.
 8. An observation instrument according toclaim 4, characterized by the fact that the gyroscopic system isassociated with two torquers of which one is provided with a rotorfastened to inner gimbal of said system and the other with a rotorfastened to the associated outer gimbal, said torquers having theirstators fastened to the housing containing said system.
 9. Anobservation instrument according to claim 4, characterized by the factthat the optics thereof include an erecting prism movably mounted on theoptical path and slaved to the combined motions of the housing and thecase about their axes whereby to eliminate image run-out.
 10. Anobservation instrument according to claim 4, characterized by the factthat the inner gimbal of the gyroscopic system is mounted on horizontalpivots, the outer gimbal being mounted on verticla pivots, the frontmirror being supported by said inner gimbal at a position causing it toprovide off the incident optical beam a reflected beam which has itsaxis co-extensive with the outer gimbal hinge line, the slaved positionof which is co-extensive with the hinge line of the pivotal housingwhich contains the gyroscopic system and is slaved thereto, the plane ofsaid front mirror being parallel to said outer gimbal hinge line andforming a fixed angle of 45* to the hinge line of said inner gimbal. 11.An observation instrument according to claim 4, characterized by thefact that motors for servo controlling said case and housing areassociated to synchro systems for exploiting and presetting theboresight elevation and azimuth angles from a distance.
 12. Anobservation instrument according to claim 1, characterized by the factthat it is provided with a single-objective binocular sight comprising,between the objective and the eyepieces, a rhombohedron comprising asplitter cube which splits the optical beam into two beams that travelto the two eyepieces respectively, said splitter cube being retractablymounted and being replaceable by an ordinary cube of the same thickness.13. An observation instrument according to claim 1, characterized by thefact that the field-changing selective magnification lens system is asnap-acting retractable Galilean system interposed ahead of theobjective.
 14. An observation instrument according to claim 13,characterized by the fact that the Galilean system is mounted on arocking member connected to a crank cooperating with an arm through aspring tumbler mechanism, said arm being actuated by a reversible motorand having its motions limited by stop means and fastened through a camfor actuating a switch that reverses the direction of rotation of amotor, said switch being series-connected to a further switch in themotor power-supply circuit.